Answers

2016-02-12T16:52:29+05:30
Mean = Sum of observations / No. of observations 

Mean of 36 observations = 12
Sum of 36 observations = 12 × 36 = 432

Actual sum
= Sum of 36 observations - incorrect observation + correct observation
= 432 - 74 + 47
= 405

∴ Correct mean = Actual sum of 36 observations/36 = 405/36 = 11.25

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